PROJECT SUMMARY Glaucoma is a debilitating disease, resulting in loss of peripheral vision and eventual total blindness if not treated adequately. Primary open angle glaucoma (POAG) is the most common form of glaucoma in Western and African nations. While the exact etiology of POAG remains unknown, it is clearly a group of heterogeneous disorders frequently associated with elevated intraocular pressure. Pedigree studies utilizing large POAG families are a powerful method to identify rare genetic variants that predispose individuals to glaucoma. By focusing on one family, the complexity of this disease can be reduced to a simpler form that is more likely to have one causal event. In a large POAG family we recently identified a mutation in interleukin- 20 receptor B (IL-20RB), which is predicted to impact binding of the receptor to the IL-20 family of cytokines. All affected patients in this family have high intraocular pressures (>22mm Hg). Our hypothesis is that the IL-20 signaling pathway functions to regulate aqueous outflow and the T104M mutation in IL-20RB results in defective propagation of signals in POAG patients. The aim of this grant is to gain a better understanding of how a mutation in a critical site in IL- 20RB leads to elevated intraocular pressure and ultimately to glaucoma. The trabecular meshwork is the tissue in the anterior of the eye that functions to regulate intraocular pressure. IL-20 signaling in trabecular meshwork cells will be investigated using two model systems - perfused anterior segments and mechanical stretch of trabecular meshwork cells. Binding of the IL-20 cytokine subfamily to the IL-20 type I and type II heterodimeric receptors containing the mutant T104M IL-20RB protein will be analyzed using plasmon resonance. We will determine the downstream effect of defective signaling through the mutant IL-20RB receptor using mechanical stretch of patient mutant and wild-type fibroblasts. The proposed work has great potential for leading to new insights into the function of the IL-20 family of signaling molecules in regulating aqueous outflow and intraocular pressure. This is the first step to developing improved therapy for this blinding disease.